Through-silicon via (TSV) or similar technologies require a continuous metal-containing layer to be deposited within a high aspect ratio feature on a substrate. For example, the metal-containing layer to be deposited may be a barrier layer to prevent diffusion of materials from the feature into the substrate or a seed layer which may be used as a template for filling the feature by electroplating or other suitable techniques. High aspect ratio features, for example, may include features having an aspect ratio of about 5:1 or greater. Unfortunately, the inventors have discovered that conventional direct current (DC) sputtering, such as performed in a DC physical vapor deposition (DC PVD) chamber does not provide adequate coverage to the bottom surface of a high aspect ratio feature. For example, the inventors have discovered for some metals, such as titanium (Ti), tantalum (Ta), or copper (Cu), the bottom surface coverage can be less than about 3%. The lack of continuous surface coverage in the feature can result in void formation during the filling of the feature. Further, while DC PVD process conditions can be modified to achieve acceptable bottom surface coverage, the conditions require long deposition times as well as exposing the substrate to elevated temperatures, which significantly impact the cost per substrate and undesirably expose the substrate to elevated temperatures causing undesirable diffusion of materials between existing regions of the substrate.
Accordingly, the inventors have developed improved techniques to deposit continuous metal-containing layers in high aspect ratio features.